Wordpress XML-RPC wp.newPage category parameter help.

I'm using a wordpress site. I have installed a plugin called Ninja Pages, which allows me to assign categories and tags to a "page". So what I am trying to do is assign a category to a page with wordpress's XML-RPC API. There is documentation here of a categories parameter. [login to view URL] So my question is , how do I assign a category to a Page via [login to view URL] (XML-RPC) I $params = array( 'title' => $wptitle, 'description' => $description, 'publish' => true, 'wp_author_id' => 1, 'wp_page_parent' => $wp_cats, 'wp_page_template' => '[login to view URL]', 'categories' => array($wp_cat) ); $res = $client -> query('[login to view URL]',1, $usr, $pwd, $params); $ID = $client->getResponse(); //print_r($res); if ($ID) echo '<div class="alert alert-success" role="alert">Product Posted Successfully. ID = <a href="http://'.$domain.'/wp-admin/[login to view URL]'.$ID.'&action=edit" target="new">'.$ID.'</a></div>'; I'm using the [login to view URL] Library to make things a little easier.